Apparatus for the production of a synthetic paper-like product from a polymer film

ABSTRACT

Apparatus for the continuous process for the preparation of synthetic paper by treatment of a polymer film to produce an opaque printable surface the process including treating the surface with a swelling agent followed by a coagulating agent with intermediate treatment in one or more baths containing adjustable quantities of swelling and coagulating agents, said baths being provided with overflow means leading to the preceding bath to provide adjustment for changes caused by carry-over from one bath to another by the advancing film.

1 States Patent 1 1 Tani et al.

APPARATUS FOR THE PRODUCTION OF A SYNTHETIC PAPER-LIKE PRODUCT FROM A POLYMER FILM Inventors: Kaneyasu Tani; Shiro Kawazoe,

both of Tokyo, Japan Assignee: Nippon Kakoh Seishi K. K., Tokyo,

Japan Filed: June 1, 1970 Appl. No.: 42,060

US. Cl ..425/445, 117/47 A, 1 17/60, 117/63, 117/64 C, 118/7, 118/67, 118/68, 118/419, 118/429, 134/64, 134/122, 264/343 Int. Cl. ..B4lm 5/14 D2lh 5/00 Field of Search ..1 17/47 A, 60, 63, 117/64 C; 118/7, 67, 68, 419, 429; 134/64,

References Cited UNITED STATES PATENTS 11/1967 Plambeck l7/36.7 6/1964 Ranalli ..1 17/63 8/1963 Holden ....117/63 9/1965 Holden ..117/63 8/1958 Bechtold ..1 17/36.7

1451 May 1,1973

3,515,567 6/1970 Tanietal ..117/47A Primary ExaminerMurray Katz Assistant Examiner-M. Sofocleous Att0rneyl-lenry T. Burke, Robert Scobey, Robert S. Dunham, P. E. Henninger, Lester W. Clark, Gerald W. Griffin, Thomas F. Moran, R. Bradlee Boa] and Christopher C. Dunham 57 ABSTRACT Apparatus for the continuous process for the preparation of synthetic paper by treatment of a polymer film to produce an opaque printable surface the process including treating the surface with a swelling agent followed by a coagulating agent with intermediate treatment in one or more baths containing adjustable quantities of swelling and coagulating agents, said baths being provided with overflow means leading to the preceding bathto provide adjustment for changes caused by carry-over from one bath to anotherby the advancing film.

6 Claims, 5 Drawing Figures Patented May 1, 1973 4 Sheets-Sheet 1- I Patented May 1, 1973 3,730,667

4 Sheets-Sheet 2 Patented May 1, 1973 3,730,651?

4 Sheets-Sheet 5 APPARATUS FOR THE PRODUCTION OF A V SYNTHETIC PAPER-LIKE PRODUCT FROM A POLYMER FILM BACKGROUND OF THE INVENTION The majority of films of the prior art formed from high molecular substances are transparent, unless subjected to a special treatment. It was heretofore impossible to obtain opaque films having satisfactory recording qualities through a mere incorporation of pigments in the compositions thereof, although many attempts were made to provide high polymer films with the best possible qualities desirable for recording, such as by printing and writing.

DESCRIPTION OF THE PRIOR ART The prior art includes, for instance, an opacification method which requires the addition of pigments or special additives at the time of the film formation; a method of effecting opacification by treatments such as rubbing or embossing the film surface formed; and a method which employs a solvent of a film-constituting resin to co-act with the polymer film, allowing the resin in a solvent to precipitate by including a precipitant to co-act with the resulting solution, and effecting a roughening process simultaneously with the opacification.

However, when proceeding according to the first and the second above mentioned methods, it is impossible to obtain a satisfactory surface suitable for printing and writing, since ink receptivity is not improved thereby, even when an incomplete opacification treatment is produced thereby. According to the third method mentioned above, the bonding strength of a roughened layer formed on the film surface is so weak that peeling off or powdering occurs simply by rubbing, the residue powder adhering adsorptively to the printing plate, and to the writing or printing instruments, and as a result, continuous recording becomes impossible.

Thus, in order to provide the polymer film with paper-like qualities for writing, printing and recording purposes, it is necessary to provide a film surface layer having qualities similar to paper, that is, suitable ink receptivity, sufficient opacity, a bonding strength to the substratum of the film capable of withstanding the conventional external force exerted on paper surfaces during recording, and durability of the surface to insure permanency of the recording.

The present invention provides a system with which the production of such a film may be carriedout successfully on a commercial basis, and advantageously from an economical point of view.

CROSS REFERENCES TO RELATED APPLICATIONS The present application is an improvement over the subject matter of a co-pending US. patent application, Ser. No. 610,481, filedJan. 20, 1967 now U.S. Pat. No. 3,515,567, in which the present co-inventors are co-inventors with others. The subject matter of that parent application is to be included herein by reference in support of the present disclosure.

SUMMARY OF THE INVENTION The present invention has as its primary object to provide a means for a continuous production in the manufacture of a polymer film opaque paper-like material with superior qualities for printing and writing.

Thus, the present invention provides an apparatus for effecting the swelling treatment of a polymer film, providing means for treating the surface of a transparent thermoplastic film with a good swelling agent which is capable to sufficiently swell said polymer of the film, but does not have the strength to dissolve it to a great extent. Optionally, means are provided to subject the film to a small extent to drying and/or pressing, and/or squeezing; means for applying thereafter one or more liquids; means for mixing these liquids with said swelling agent; means to apply the comixed liquids to the film surface in a series of stages in an order of decreasing swelling actions, beginning with a stage having a largest swelling action, and continuing in a decreasing order. Means are provided thereafter to coagulate in succession the resulting swollen surface layer of the previous stage with a liquid which is a nonswelling agent for the film selected and miscible with the swelling agent used in the previous stage. A bright, opaque, roughened layer on the film surface is thus produced.

The treating bath structure comprises, intermediately between a film unwinder and a film winder, means for a swelling bath stage, at least one intermediate treating bath stage, a coagulating bath stage, and an after-treatment bath stage, in series in succession.

In the swelling bath stage means are provided to charge it with a swelling agent, in the coagulating bath stage means are provided to charge it with a coagulating agent, and in the intermediate treating bath stage means are provided to charge it with a liquid mixed with a swelling agent and a coagulating agent When it is desired to provide a plurality of intermediate treating bath stages, means are incorporated to adjust the composition, of the swelling agent in the firstintermediate' treating bath to one-third to two-thirds of the swelling bath, while with regard to the subsequentsecond intermediate treating bath, the third intermediate treating bath and the nth intermediate treating bath, etc the concentration of said swelling agent is regulated through an adjustment means so as to become 178 178 2 W" of the concentration of the first intermediate treating bath, respectively.

And each one of these bath stages is provided withat least one assembly of a guideroller and a squeezing roller. intermediately between the swelling bath and the intermediate treating bath stages there is provided a device with which to effect to a small extent drying of the swollen layer and/or to effect pressing and/or squeezing. Also intermediately between the after-treating bath stage and the winder, there is provided a final drying device, whereby the film fed from the film winder is wound around the winder by these rollers and the drying and/or the squeezing devices.

Means are further incorporated to offset the amount of loss of a treating agent caused by the carry over on to the film during transportation between the swelling bath and the after-treating bath.

The feeding of treating liquids to be consumed in the course of conducting the inventive treatment is effected separately by three individually provided means, namely, the swelling bath, the intermediate treating bath-coagulating bath, and the after-treating bath, respectively.

A treating liquid previously prepared according to the quality of a product to be obtained, is successively fed to the swelling bath and to the after-treating bath in such a way as to maintain the liquid level constant that is to replace the amounts consumed.

In the meantime, in regard to the feeding into the intermediate treating bath and coagulating bath, a treating liquid is fed from the coagulating bath to the nth the second and the first intermediate treating baths in succession by overflow as described hereinafter. The above feeding is conducted continuously so as to maintain the amount of liquids and compositions always constant.

The respective amount of loss is here adjusted by a system which hereinafter for the purposes of disclosure and claims will be identified as the liquid level control system. The loss occurring between the intermediate treatment bath and the coagulating bath is corrected so that the initially established composition of the respective bathstages arecontrolled in the first intermediate treating bath Stage to approximately twice the amount of the liquid carried over by the film advancing to said coagulating bath stage as it is supplementarily fed between the coagulating bath stage, the final bath stage through the intermediate treating bath stages in regular succession according to a means of an overflow system operating in the direction opposite to the direction of the film thus wound. Means are provided to determine the amount of the coagulating agent required for effecting the overflow and to supply it to the coagulating bath stage while being controlled in proportion to the carried-over amount.

Means are further provided to maintain the bath stages at temperatures below the heat softening point of the film throughout. Means are provided to subject the film forwarded from the unwinder to the swelling bath stage. The formation of a swollen layer results on the surface thereof. Means are also provided to sub stitute gradually for the swelling agent present in the swollen layer, the intermediate treating agent, and the coagulating agent, while the film passes through the intermediate treating bath stage and the coagulating bath stage. Thereafter, means are provided in the aftertreating bath stage for desired additional treatments, such as an antistatic treatment means, dyeing means or the like, and drying means, and thus, the treated film is wound around the winder in the form of a paper-like product having an opaque porous paper-type surface.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional side view schematically illustrating as an example an embodiment of the apparatus according to the present invention;

FIG. 2 illustrates the successive stages of the film relative to the respective treatment tubs;

FIG. 3 is a schematic view of a supplemental device required for providing the finished paper-like product with gloss;

FIG. 4 is a block diagram illustrative of the automatic controls of the composition of the first intermediate treating bath stage by use of a gas chromatography;

and also the solubility thereof.

TABLE I Substrate Swelling agent Temp. Solubility resin (weight parts) (C) (weight acetone (100) 30 0.04 acetone (90):carbon 25 0.21 tetrachloride (10) acetone ():carbon 25 7.86 tetrachloride (10) High impact (50): (30) 25 12.58 polystyrene MIBK (95):MeOH (5) 40 0.29 (90): (10) 40 0.13 (85):" (15) 50 0.85 (20) 30 0.02 CHN (70):MeO1-l (30) 30 1.86 acetone (100) 20 0.04 'M1BK(90):Me0H (1O) 30 0.54 (80): (20) 30 0.03 P ystyrene benzene (90):MeOH (10) 25 12.00

MEK (100) 40 1.65 (100) 50 3.91 MIBK (100) 40 0.73 (100) 50 0.84 THF (100) 25 5.00 (80):MeOH (20) 25 1.87 Polyvinyl (92):Water (8) 30 0.56 chloride (88):Water (12) 30 0.20 CHN 25 2.71 (75 )zlPA (25) 25' L35 ('s()90):Water (5)1MeOH 30 0.90 {):Water (75 )2 30 0.20 MeOH (75) I (80):Water (10): 30 0.07 MeOH (l0) THF (90):MeOH (10) 20 0.36 (80): (20) 20 0.18 Vinyl (70): (30) 30 0.09 chloridevinylidene (70): (30) 40 0.44

FIG. 5 illustrates details of the film driving system of FIG. 1, according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the first place, an explanation is hereby given in regard to polymer films and treating agents suitable for processing in the apparatus of this invention.

In principle, a polymer film may be employed, disregarding the particular kind thereof, the presence or absence of pigments and/or additives therein, and whether it is oriented or not, as long as it is a synthetic resinous film, capable of effecting swelling. However, in general, in view of the nature of the resin, a polystyrene resinous film and a polyvinyl chloride film are preferred for treatment by the present apparatus as long as they meet the intended requirement.

As a swelling agent for the formation of a swollen layer on the surface of such a polymerfilm, any liquid which is capable of effecting the swelling of said film will suffice. Nevertheless, in order to obtain an opaque, porous layer, excelling in surface bonding strength, such a liquid should be a non-solvent, or a poor solvent, of the film material on hand.

The permissible solubility of the film resin by the swelling agent is determined on a selective basis in accordance with the types of the film resin and conforming with the following Table 1 which exemplifies a combination of typical polymer films with a swelling agent,

chloride copolymer dioxane (W) 20 L24 (95):MeOH 20 0.52 (90):" (I0) 30 0.08 (80):" (20) 30 0.03

Solubilizing capacity (percent by weight) refers to the maximum amount of the polymer film resin which can be dissolved in the swelling agent at an operational temperature.

The abbreviations in the above table denote the following:

MIBK methyl isobutyl ketone MElK methyl ethyl ketone THF tetrahydrofuran MeOH methyl alcohol IPA isopropyl alcohol CHN cyclohexanone A coagulating agent to be charged into a coagulating bath is selected among liquid agents belonging to the single component system or to the multiple component system, which has good miscibility with the swelling agent and does not cause dissolving or swelling of the film-constituting resin used.

Table 2 exemplifies some of the typical coagulating agents suitable for combination with the swellin agents shown in Table l.

TABLE 2 Film resin Swelling agent Coagulating agent Polystyrene MlBK ROI-l Cl-IN ROH acetone ROH; water benzene ROH Polyvinyl MEK ROH chloride MIBK ROH THF ROI-l; water CHN OH dioxane ROH; water (In the above table, MIBK, MEK, MeOH, CI-IN and THF have the same definitions as in Table l, and ROH represents an aliphatic saturated alcohol having carbon atoms in the range of one to four.) y

Into the intermediate treating bath stage is charged a mixture of a liquid agent mixed with a swelling agent and a coagulating agent. When the intermediate treating bath stage is a single bath stage, the concentration of the swelling agent is adjusted to one-third to twothirds of the concentration of the swelling bath. When the intermediate treating bath stage includes a plurality of bath stages the concentration of the swelling agent in the first intermediate treating bath stage is the same as in the case of the single bath stage. Likewise, the concentrations of the swelling agent as to the second, third, nth intermediate treating bath stages are adjusted to 1%, k and W respectively of the concentration of the first intermediate treating bath stage in regular succession.

Thus, one of the reasons why. an arrangement is made to provide a gradation to the concentration of the swelling agent in the intermediate treating bath is to impart to the paper-like product a high surface strength. Another reason is to warrant the maintenance of a uniform composition in each bath to be consumed in the course of carrying out a successive treatment And still another reason resides in the reduction of production costs by means of effecting the repeated use of the coagulating liquid.

The number of intermediate treating bath stages and the overall length thereof are determined on the basis of a desired production capacity and quality.

The aforementioned arrangement of the film, the charging of the respective treating agents and liquid level controls can be effected automatically as well as continuously.

FIG. 1 exemplifies a working embodiment of the apparatus according to the present invention, in which a bath structure is shown with four intermediate treating baths, and with the controlling system thereof.

The film 2 on the film unwinder 1 is transported in sequence to a swelling bath stage 10, a first intermediate treating bath stage 20, a second intermediate treating bath stage 30, a third intermediate treating bath stage 40, a fourth intermediate treating bath stage 50, a coagulating bath stage 60, and an after-treatment bath stage by a guide roller 3, a driven roller 4, equipped with a film speed adjusting mechanism, a guide roller 5, and tension rollers 6, 7 and 8, respectively. After a required treatmenthas. been accomplished, the film 2 is dried by a drying device 80, so that it is wound around winder by way of guide rollers 91, 92 and 93, respectively.

The particulars of the bath stages are shown in FIG. 2. The overall length of a bath stage can be determined by trial and error, but preferably on the basis of a time period required for the formation of a swollen layer, a time period required for effecting the coagulating treatment of the swollen layer and the running speed of the film. For instance, a polystyrene and polyvinyl chloride film speed preferably is about 30-100 m/min. All the bath stages and rollers, excepting the squeezing rollers 64 and 74, are preferably for example, made of stainless corrosion resistant. In order to prevent the film from suffering possible damage and to assure a smooth transportation thereof, the stainless steel rollers are preferably coated with such as polytetrafluoroethylene.

The swelling bath stage 10 is installed inside a constant temperature tank 17, having an inlet for the swelling agent 11, and an outlet 12. Both inlet and outlet are connected with a pipe which is in communication with the swelling agent feed tank T-l, respectively.

Inside the bath stage, there are installed a guide roller 13 and a clipping roller 14, provided with upward and downward movement controls for adjusting a treatment time. Further, in the upper portion of said bath stage is mounted a pressing-squeezing. roller 15 to squeeze out the surplus swelling agent carried over onto the film. A receptacle 16 for receiving droplets formed bysaid squeezing is provided. The film passing under the pressing-squeezing roller 15 thereafter passes into the dryer 18 for an intermediate drying as shown in FIG. 3, if it is desired to provide a finished paper like product with a good surface bonding strength and gloss, prior to subjecting it to a treatment in the first intermediate treating bath stage.

In the intermediate treating bath stages 20, 30, 40 and 50, the bottom portions are provided with inlets and outlets for charging and discharging the treating liquid 21, 31, 41 and 51, respectively.

Each one of these feed outlets is branched, and they are provided with feed valves 25, 35, 45, and 55, and with outlet valves 26, 36, 46, and 56, respectively, all of which are connected with feed tanks T-Z, T3 and with pipes which are in communication with a waste liquid tank T-6.

In between the intermediate treating bath stages and between the fourth intermediate treating bath stage 50 and above the upper wall adjacent to the coagulating bath 60, there are installed downward flow outlets of the liquid to the preceding bath stages, numbered 32, 42, 52 and 62, respectively. It is the purpose of said downward flow outlets to control the liquid level of the treating bath and to provide the treating liquid to the preceding bath in regular succession by the overflow method. For this purpose the level of the downward flow conduit system is so arranged that it is gradually elevated in direction of transportationin regular succession. The treating liquid is flowing downwardly from each bath stage into the tank of the respective preceding bath stage,

In the respective intermediate treating bath stages, there are installed guide rollers 23, 33, 43, and 53, in such an arrangement as to accommodate two runs of films. In the upper portions of the respective bath stages, there are installed guide rollers 24, 34, 44, and 54, which function also for squeezing out the treating liquid carried over on the films.

In the bottom portion of the coagulating bath stage 60 and of the after-treatment bath stage 70, there are installed feed inlets 61 and 71 for the coagulating agent.

and after-treating agent, and also valves 56 and 72 therefor. Said feed inlets are connected with pipes which are in communication with a feed tank for the coagulating agent and after-treating agent, through respective valves.

Similarly, in the upper wall portion of the after-treatment bathstage, there is installed an overflow outlet 76 which serves to control the liquid level of said treating agents. Inside these baths there are installed guide roller 63 and 73 in such an arrangement as to accommodate two runs of the films. Also, in the upper portions of the respective bath stages, there are installed squeezing rollers 64 and 74, made of stainless steel roller and rubber roller, squeezing rollers 64 and 74, and receiving receptacles 65 and 75 for receiving droplets resulting from the squeezing operation.

- A drying device. 80 is installed, having a length required for effecting the final drying of the film, conventionally ranging from about 30 to 50 m. The employment of a hot air drying method meets the purpose. The drying is carried out under a constant temperature, up to the softening temperature of the film. In order to prevent the lowering of opacity, preferably two to three temperature differences in the respective zones are provided, namely, a low initial temperature at the initiation of drying, gradually increasing to high toward the outlet portion. Winder 90 is run by a variable speed motor so that the film tension can be varied.

The charging of the treating liquid into the respective baths is carried out in the following manner.

In effecting the charging of a swelling agent into the swelling bath stage, the swelling agent from the tank T-3 and from the coagulating agent from tank T-2 are introduced into a metering pump P-l, from which they are fed by way of feed inlet 95 to an adjusting tank T-l, equipped with a constant temperature tank 94 in the initially determined concentration. The treating liquid adjusted to the desired composition and temperature by means of the adjusting tank T-l is fed from the outlet 96 to the feed inlet 11 in the swelling bath 10 by the pump P-2. When the treating liquid reaches the predetermined level, it will overflow through a discharge outlet 12 and is directed into the tank T-1 through inlet 97. The completion of charging is detected by means of a liquid level controlling device 98 provided in the adjusting tank T-l, which has an electric signal output of said completion. This impulse is transmitted to the control valve 99 of pump P-l, at which time the valve is closed, and thus the feeding of the treating liquid comes to a stop. The circulation of the treating liquid between tank T-1 and the bath stage 10 is continuing by means of pump P-2. In case the swelling agent is consumed according to the progress of the treatment, the liquid level of the adjusting tank T-l is lowered in proportion to the amount of the swelling agent consumed. The lowering of the liquid level is detected by the level control device 98 and the impulse is transmitted to the control valve 99, which is caused to open. At this point, a predetermined ratio of the treating liquid is supplementarily charged into the adjusting tank from the pump P-l, until the liquid level of the adjusting tank has reached the desired level. This operation is repeated continuously. Through the adjusting tank T-l and the constant temperature tank of the swelling bath stage 10, either cold or warm water is circulated to maintain a predetermined temperature.

The treating liquid for the intermediate treating bath stage is charged respectively according to the status of the aforementioned composition. Means are-provided to conduct the coagulating agent for the coagulating agent tank T-2 and the swelling agent for swelling tank T-3 to a first intermediate treating bath stage to a flowmeter M-2 by means of pumps P-4 and P-5 respectively so that the concentration of the swelling agent becomes approximately one-third to two-thirds of the composition of the swelling bath. Thereafter, a desired amount of the coagulatingagent and of the swelling agent are determined and fed to the first intermediate treating bath in an amount to cause an overflow of the surface level so that the liquid agents overflow from the feed inlet 21 thereof. In this case, the respective valves installed in the feed conduits are controlled for the purpose of feeding said liquid agents. In the second place, the charging operation of the treating liquid agents to the second, third and fourth intermediate treating bath stages is carried out by following the same operationas observed in the preceding paragraphs. That is,-the

coagulating agent and the swelling agent are estimated by means of the flowmeter M-2 so that the concentration of the swelling agent becomes approximately k, A and A of the concentration of the first intermediate treating bath. Thereafter the liquid agents are fed to the first intermediate treating bath to such an extent of its surface level that the liquid agents overflow out of the feed inlets 31, 41, and 51, respectively.

The coagulating agent for the coagulating tank T-2 is charged into the coagulating bath by means of pump P-4 to such an extent of its level, that said liquid agents overflow after measuring or without measuring said coagulating agent by means of the flowmeter M-l.

Thus, after the treating liquid agents have been charged into the intermediate treating baths and coagulating baths, all discharge valves, except for the one belonging to the discharge liquid system for the overflowing amount from the first intermediate treating bath 20, and the feed valves other than those to coagulating bath 60, are closed. At this point, the automatic control will commence working.

The Coagulating Bath System comprises:

A coagulating agent tank T-2;

pump P4;

automatic control valve A-3;

flowmeter M-1; and

a coagulating bath stage 60.

The First Intermediate Treating Bath System comprises:

A coagulating tank T-2;

pump P4;

automatic control valve A-l; The first intermediate swelling agent tank T3, treating bath stage 20 pump P-5;

automatic control valve A-2 The automatic control in such a system controls the amount of the respective treating liquid agents required in the treating operation and also adjusts the composition of said agents.

The coagulating bath system requires the coagulating agent in an amount twice of that which is carried over in adhesion adsorptively on the film when transported to the coagulating bath through the flow amount controlling means of automatic control valve A-3. The control by means of automatic valve A-3 is carried out in proportion to the film running speed measured by the driven roller 4 which also serves as indicating the film running speed. In other words, the amount of the treating agent to be carried over in adhesion adsorptively on to the film and the film running speed are approximately in direct proportion to each other. And accordingly, it will completely suffice to calculate the relative proportion thereof prior to commencing the operation, so that the control valve A-3 effects automatic opening and closing in proportion to the film running speed. I

Thus, the feeding to the coagulating bath approximately is twice the amount of liquid agent to be carried over to said coagulating bath and by effecting an overflow of the coagulating agent from the coagulating bath to the fourth, third, second and first intermediate treating baths in regular succession, the concentration of the swelling agent caused by the overflow is gradually diluted by the overflowed coagulating agent, and because the added amountof treatingliquid successive ly overflowed into the preceding bath, the capacity and composition of the respective baths are maintained always constant.

As an example,

the following relations are established between the respective intermediate treating baths, and from the following table, it will beunderstood thatthe concentration and amount of liquid can be maintained constant.

TABLE Bath 2nd 3rd 4th Concentration(%) 20 l Amt. carried 5 5 5 over from the preceding bath Amt. returned l0 l0 from the succeeding bath (l/min) In the meantime, the treating liquid overflowed from the first intermediate treating bath flows into an intermediate tank T-S, and is then poured into a waste liquid tank T-6 by means of pump pressing-squeezing 3.

The amount of the swelling agent to be carried over to the first intermediate treating bath from the swelling bath 10 may vary depending on the extent of squeezing and drying derived, in case a pressing-aqueezing roller and/or an intermediate drying device 8 are installed in said carry-over stage. And in this case, the composition of the first treating bath will be subjected to a variation according to a time lapse, unless an adjustment of the composition is made.

Accordingly, it is necessary to make such a compositional adjustment in regard to the first intermediate treating bath, depending upon the need.

When the detecting means 29 establish that the composition exceeds the permissible range the adjustment means introduce into the waste liquid system of the first intermediate treating bath 20 the required components. The output detecting signal actuates automatically the control valves A-1 and A-2. Gas chromatography or a reflectometer is used for the compositional detection.

In the example shown in FIG. 4, gas chromatography is used as the detecting device. Means are provided to introduce overflow liquid from the first intermediate treating bath to a gas chromatograph A, effecting the detection of a variation. Whenever the concentration of the swelling agent drops below the upper and lower limits in the range of one-third to two-thirds of the swelling bath composition, an electric output creates an electrical signal, which is amplified by an amplifier B, which in turn opens or closes the control valves.

C given in FIG. 4 represents an air purge system which is operated according to the above-mentioned electrical signal. Each one of the control valves is put into a closed position in case the concentration of the swelling agent for the first intermediate treating liquid is in a permissible range. of concentration. When the swelling agent concentration is in excess of the upper limit of up to two-thirds of the swelling bath, the con- .trol valve A-l is opened, while the control valve A-2 opens when the concentration drops below the lower limit. Thus, the. feeding of the coagulating agent and of the swelling agent continues respectively, until such time as the concentration of the swelling agent has reached the predetermined range. i

In the after-treatment bath stage the tank is filled with a treating agent, the concentration of which is adjusted according to the predetermined requirements. In the operation the treating agent is continuously charged through the valve 77 of the tank T4.

The apparatus of this invention is driven by a system of two driving mechanisms, as is shown in FIG. 5.

On of the driving mechanisms incorporates a film winder 90, driven for instance by a torquemotor, TM, actuated in proportion to the film tension. Other driving means drive the film driven roller, a swelling agent dipping roller, guide rollers for the intermediate treating bath stages, the coagulating bath stage and aftertreatment bath stage, and squeezing rollers for the coagulating bath stage and the after-treatment bath stage. The transmission of the driving power to the respective parts mentioned above may be effected from the main driving shaft, shown driven by an electric motor M, via transmitter PIV.

Various conditions are required for producing a polystyrene paper-like product by the use of the apparatus of this invention.

As is illustrated in FIG. 2, the extreme end of the film is positioned on the unwinder, for instance, by a carrier chain, and is then fixed on to winder 90. In order to prevent over-swelling of the film and any spoilage on account thereof, the film positioning on to the dipping roller 14 inside the swelling bath 10 should be effected immediately prior to the commencement of treatment. The required swell and the over-swelling can be established because the web will be cut off when overswelling.

After the film has been so arranged, the apparatus may be driven under automatic control. Then simulataneously, the formation of a swollen layer on the surface of the film, the intermediate treatment, the coagulation, the after-treatment, and the drying process can be effected continuously and automatically, whereby the resulting film will be wound around the winder 90 in the finished form as a paper-like product.

Table 3 shows the composition of the respective baths for the paper-like end product from polystyrene when opacity in excess of 40 percent is desired by use of methyl isobutyl ketone (MIBK) as a swelling agent and of methyl alcohol (MeOH) as a coagulating agent. Column A represents results obtained without employing the intermediate drying stage and the pressingsqueezing stage, while Column B represents the results obtained by including'an air drying and/or a squeezing stage, until the amount of the swelling agent present in the swollen layer has become more or less 50 to 10 percent thereof immediately after the formation thereof.

TABLE 3 Liquid A B Composition Bath MIBK MeOl-l MlBK MeOH swelling bath 50-85(%) 50-15(%) 80-l00(%)20-0(%) first intmed. 17-56 3-43 27-67 73-33 treatmt. bath second int. treat. 8-8 92-72 14-34 86-66 bath third int. treat. 4-14 96-86 7-17 93-83 bath fourth int. treat. 2-7 98-93 3-8 97-92 bath coagulating -4 100-96 0-4 100-96 bath after-treatmt.

. bath 0.5% methyl alcohol solution of alkyl sulfonate antistatic agent (Elenon) Table 4 exemplifies the composition of the respective baths when a swelling bath composition MIBK by 85 percent, correlated with column A of Table 3 is used.

TABLE 4 bath stage bath stage composition swelling bath MlBK (85) MeOH (l5) first int. treat. bath (50) (50) second int. treat. bath (25) (75) third int. treat. bath (l2) (88) fourth int. treat. bath (5) (95) coagulating bath (0) (I00) after-treatment bath 0.5% methyl alcohol solution of alkyl sulfonate antistatic agent (Elenon l9M) Further with reference to the bath compositions shown in Table 4, means are provided to preset a variable swelling treatment for a time period required before the coagulation of the formed swollen layer in proportion to the film transporting speed. The duration of the varying swelling treatments is shown here at the film running length in the swelling bath of 1.5 m. The overall running length of the film, its opacity, brightness and the gloss of the finished paper-like product, and the thickness of the opaque layer formed are shown in Table 5 in their interrelationships.

Table 6 presents additional test results, when a film of a width of 1,000 mm was tested in the apparatus of this invention.

TABLE 5 time for thickness of film swelling opacity bright gloss opaque speed treatment ness layer m) (s (l 36 2.5 90 93 4 39 45 2.0 85 92 4 32 1.5 4 26 72 1.2 70 8O 4 20 I00 0.9 60 75 4 10 As seen from Table 5, when the overall length of the film in the swelling bath, the bath composition and the temperature are made constant, the thickness of the opaque roughened layer of the paper-like product, which is to be obtained in proportion to the film speed (period of time required for carrying out the swelling treatment) can be controlled, while the roughened layer will effect the opacity and brightness. The gloss is very little influenced by the swelling treatment time.

When the treatment is to be carried out under the aforementioned conditions, the amount of a treating solution to be carried over into the coagulating bath hardly varies depending on the film speed, as is illustrated in table 6.

TABLE 6 film speed carryover amt. amount picked up (m/min.) (l/min.) (g/m) The amount of the coagulating liquid to be supplementarily fed from the coagulating bath to the fourth intermediate treating bath by means of the overflow method is controlled by the predetermined film speed and the loss in the required concentration which is to be supplemented, taking into account the amount of liquid carried over from the coagulating bath to the after-treatment bath, and in accordance therewith the coagulating liquid is fed through the feed valve to the coagulating bath stage.

As is shown in Table 5, the above example results in obtaining a paper-like material having little gloss. In order to increase the degree of gloss, it will suffice to incorporate between the swelling bath and the first intermediate treating bath a pressing-squeezing stage of the swollen layer and/or an air drying stage may be interposed. In this pressing-squeezing stage means to adjust the pressure exerted on the pressing-squeezing roller by the film are actuated while the air drying is effected by means of blowing air toward both sides of the film.

Table 7 represents the relationship between the amount of the swelling agent contained in and remaining on the swollen layer, immediately after the formation-thereof, and the gloss obtained, as a result of squeezing and/or drying.

TABLE 7 swelling agent amt. of swelling gloss contained agent remaining (gl (M 80 100 r 3 73 86 5 t 65 77 7 50 59 I 37 44 I 30 35 2O 25 29 25 22 26 30 20 24 35 The composition of the agents exemplified above is expressed in percent by weight.

An optional antistatic treatment stage was incorporated in the test results shown in FIG. 7 with the film running length in the after-treatment bath stage being 3.5 m. This treatment stage resulted in bringing the amount of static electricity below 3 mg in each case. For the final drying, a warm air drying apparatus was used, having temperature zones of 45C, 60C and 75C, spaced from the film inlet to the outlet thereof, each having a length of 20 m, for each one of said different temperature zones, the total length being 60 m. The thickness of the opaque layer was measured on the basis of a microscopic photograph of a cross-sectional view of the finished paper-like product. Brightness and opacity shown were the values measured'by use of Hunter Multi-Purpose Reflectometer. Gloss denotes a value measured by a gloss-meter GM-,3. The extent of static electricity accounts for a value resulting from measuring by chemical balance an amount of decrease caused by the accompaniment of attraction of static electricity observed when a test piece having the size of 25 mm X 40 mm was brought as near as 14 mm off the surface of a filter paper for chemical analytical purpose, after said test piece was rubbed 20 times with a piece of cotton cloth under the conditions of 25C and 65%RH. It should be noted that the value shown will be safely put to practical use when it is below 10 mg.

The treating agent contributing to effect the coagulating treatment can be included in consecutive order in every intermediate treating bath stage according to the apparatus of this invention. The repeated use of the coagulating agent is not only extremely advantageous economically, but also is epochmaking in that an unexpected effect is achieved by using the coagulating agent in the industrial production of a synthetic paper-like product, since the control of this use can be carried out continuously and automatically.

In the detailed explanation given in the preceding pages, an apparatus incorporating therein four intermediate bath stages has been described. However, it should be noted that the number of the bath stages can be increased or decreased, depending on the requirements of a particular case. It should also be noted that in the apparatus of the invention the number of guide rollers in the bath stages, the stage of preparation of a treating agent, the feed inlets and outlets for feeding and discharge, the depth of bath tubs, the dimensions thereof, and the other parts, may be modified into different correlated structures.

The after treatment bath stage optionally includes additional stages, such as an antistatic treatment stage, t

a dying stage, an embossing stage, and similar.

We claim:

1. An apparatus for imparting opacity, printability and writability to a polymer film, comprising in com bination:

an unwinder of a film web and a winder adapted thereto for receiving and rewinding the treated film thereon;

and positioned between said unwinder and winder, in series and in the following order:

means for holding a swelling bath, including means to charge said bath with a swelling liquid for said polymer film,

means for holding at least one intermediate treating bath including means to charge said bath with a liquid which is a mixture of a swelling agent and a coagulating agent for said polymer film,

means for holding a coagulating bath including means to charge said bath with a coagulating liquid for said polymer film,

means for holding an after-treatment bath, including means to treat said polymer film with additional agents and g a dryer unit; there being means for forwarding said film from the unwinder to the winder through said baths and unit, and means including detection means and control means to monitor changes of volume and concentration in the said intermediate and coagglating liquid baths and to replenish the liquid content thereof with liquid of a predetermined concentration, said control means including overflow means whereby a a part of liquid within each bath is returned to the immediately preceding bath, thereby providing an adjustment for the change caused by the carryoger of a part of liquid within said each bath by the advancing film.

2. An apparatus according to claim 1, further comprising means to withdraw continuously the liquid overflow fromthe first intermediate bath located adjacent to the swelling bath from the apparatus.

3. An apparatus as claimed in claim 1, said at least one intermediate bath being a plurality of baths further comprising means to control theconcentration'of the treating liquid: i

in the first intermediate treating bath between onethird to two-thirds of the swelling agent in said first swelling bath; i

in the second intermediate treating bath at one-half of the swelling agent in the first intermediate bath;

in the third intermediate treating bath to A and proportionally so on to the nth intermediate treating bath, which isto W 4. An apparatus accordingto claim 1, further comprising a squeezing roller unit disposed intermediately between said swelling bath' and the intermediate treating bath located adjacent thereto.

5. An apparatus according to claim 1, further comprising an intermediate dryer disposed between said swelling bath and the untermediate bath located adjacent thereto.

6. An Apparatus according to claim 1 further comprising a squeezing roller unit and an intermediate 

2. An apparatus according to claim 1, further comprising means to withdraw continuously the liquid overflow from the first intermediate bath located adjacent to the swelling bath from the apparatus.
 3. An apparatus as claimed in claim 1, said at least one intermediate bath being a plurality of baths further comprising means to control the concentration of the treating liquid: in the first intermediate treating bath between one-third to two-thirds of the swelling agent in said first swelling bath; in the second intermediate treating bath at one-half of the swelling agent in the first intermediate bath; in the third intermediate treating bath to 1/2 2 and proportionally so on to the nth intermediate treating bath, which is to 1/2 (n 1).
 4. An apparatus according to claim 1, further comprising a squeezing roller unit disposed intermediately between said swelling bath and the intermediate treating bath located adjacent thereto.
 5. An apparatus according to claim 1, further comprising an intermediate dryer disposed between said swelling bath and the untermediate bath located adjacent thereto.
 6. An Apparatus according to claim 1 further comprising a squeezing roller unit and an intermediate dryer disposed intermediately between said swelling bath and said coagulating bath. 